The present invention relates generally to hand-held cable tie tensioning and severing tools, and more particularly, to an improved tool for reliably installing or applying high tension to flexible cable ties and severing the ends thereof without over-tensioning the cable ties.
As is well known to those skilled in the art, cables ties are typically used to bundle or secure a group of elongated articles, such as electrical wires and cables. Cable ties of conventional construction include a cable tie head and an elongated tail extending therefrom. The tail is wrapped around a bundle of articles and thereafter inserted through a passage in the head. The head of the cable tie typically supports a locking element that extends into the head passage and engages the tail to secure the tail to the head, or at least prevent rearward travel of the tail back through the passage so as to disengage the head.
In practice, the installer manually places the tie about the articles to be bundled, inserts the tail through the head passage and then manually tightens the tie about the bundle. At this point, a cable tie installation tool may be used to tension the cable tie to a predetermined tension about the bundle. With manually powered tools, one or more grip strokes may be needed to sufficiently tension the tie, depending upon, among other things, how much tension is desired. Once the strap tension approaches the desired level of tension, as predetermined and reflected in the tension setting level of the tool, the tool severs the excess tail portion from the tie, i.e., that portion of the tail which extends beyond the head of the cable tie.
With pneumatic tools, a single depression of a button or the like is typically used to activate pneumatic pressure to tension the cable tie to the predetermined tension. Similar to the manually powered tool, once the predetermined tension setting level is reached on a pneumatic tool, the tool severs the excess tail portion from the tie.
Most prior tools, though capable of tensioning and thereafter severing the excess tail portion of the cable tie, have several disadvantages associated therewith which, either singularly or plurally, increase the frequency of operator injuries, and increase the frequency and magnitude of tool degradation and failure. For example, the cast metal body tool disclosed in U.S. Pat. No. 3,661,187 to Caveney, et al., represents what is now a conventional linkage style tensioning and severing assembly. Relative to more recent designs, the tool housing shown in the '187 patent is not very ergonomic, though the linkage design is extremely durable. The cast metal body provides apertures in which pins or shafts are secured to mount and provide pivot points for the many linkage arms. Since the linkage assembly style of tensioning and severing generates such high forces at the pin locations and cantilevered loads on the linkages, the durable cast metal body becomes a necessity for reliable operation and to keep the pins from distorting the housing and deleteriously migrating. Using the stored energy principle of a partially compressed spring, accurate and predictable severance breakaway is achieved when the pins cannot move and the arms move through their intended movements. A disadvantage of the cast metal body, however, is that it requires a significant number of manufacturing steps, driving the cost higher.
Other prior art examples include U.S. Pat. Nos. 4,793,385, 4,997,011, and 5,492,156, all to Dyer, et al., which disclose an ergonomically motivated plastic bodied tool. A conventional linkage style arrangement similar to that disclosed in Caveney, et al., is used, but the tension adjustment assembly has been moved to the top of the tool. In this location, the operator can more easily see and manipulate the tension adjustment knobs. Additionally, a more deeply curved handle is shown, though in practice the foam handle cover used therewith yields a result which is not very ergonomic. The major disadvantage of this tool is the combination of a high angular force linkage design and a plastic body. Due to this combination, the tool is not nearly as durable as some previous designs. The high off-center loading forces of the linkage design are exerted on the pins mounted in the plastic body. As the number of cycles of the tool increases, the pin holes become elongated and allow the pins to migrate or wobble. Consequently, the uniform severance point that is normally achieved with the linkage style design becomes unpredictable, and accurate and consistent tensioning is not possible. Ultimately such a tool will fail to produce reasonably repeatable results, after which the tool must be discarded.
Another prior art tool is described in U.S. Pat. No. 5,915,425 to Nisson, et al. It proposes to solve several ergonomic disadvantages of prior tools by providing an adjustable grip size, a rotatable nose, and reduced recoil shock/vibration. While attempting to overcome these disadvantages, the plastic bodied tool disclosed in the '425 patent incorporates a more variable tensioning and severing assemblies than those previously disclosed. In practice, the design has resulted in a poorly performing tool that is not durable, is subject to tensioning inconsistences between tools, fails to provide a distinct and uniform severance point, is unable to accurately calibrate its tension setting, and includes a fragile tension setting device.
Yet another tool is described in U.S. Pat. No. 6,206,053 to Hillegonds. The manually activated and manually powered cable tie tensioning and severing tool described therein provides numerous advantages over prior designs and permits users to quickly and economically apply successive ties under uniform predetermined tensions, resulting in consistent cut-off heights. Additionally, the design includes a tension rod and generally aligned cutting mechanism sleeve, and a concentrically/coaxially mounted restraining means that reduces off-center loads and thereby increases the cycle life of the tool. Despite its advantages over many prior designs, however, the tool still requires manual power to tension the cable ties. Additionally, this prior design utilizes many parts and thus has a somewhat higher manufacturing cost than other designs, particularly those using external power. As the tool embodiments shown and described in U.S. Pat. No. 6,206,053 include some structures and/or assemblies that are similar or identical to specific structures and/or assemblies of the tools described herein, the entire disclosure of the '053 patent is incorporated herein by reference.
There is therefore a need in the art for a cable tie installation tool which is ergonomic, reliable, durable, consistent, lightweight, cost-efficient and externally powered.